Chronic fatigue syndrome (CFS) has been diagnosed on the basis of the clinical symptom. More specifically, the following symptoms of (1) and (2) are defined as major criteria in CFS diagnostic criteria made by Ministry of Health and Welfare (Nonpatent document 1 below).                (1) continuation of six months or more of such heavy fatigue condition that daily life is remarkably damaged, or repeated recurrence of such condition (such condition is seen in 50% or more of the period).        (2) the symptom is different from known physical disorders and mental depression, as a result of clinical history, physical findings and examination findings.        
Moreover, the following criteria of symptoms and physical findings are defined as minor criteria in CFS diagnostic criteria made by Ministry of Health and Welfare.
A) criteria of symptoms (continuation of six months or more of the following symptoms, or repeated recurrence of such symptoms);                1. subfever (axillary temperature 37.2-38.3° C.) or chill, 2. pain in the throat, 3. swelling of cervical or axillary lymph nodes, 4. reduction of muscular power due to unclear reason, 5. pain or discomfort in the muscle, 6. continuation of 24 hours or more of feebleness of the whole body after light work, 7. pain in the head, 8. mobile pain in the joint without swelling and rubor accompanied, 9. psychiatric disorder (the following one or more); photophobia, transient scotoma, amnesia, irritability, confusion, thinking reduced, poor concentration, and depression, 10. sleep problem (excess or shortage of sleep), 11. the major symptoms appear in several hours to several days at the stage of development.        
B) criteria of physical findings (two or more confirmations of the following physical findings by the doctor at the interval of at least one month or more);                1. subfever, 2. non-transudative inflammation in the throat, 3. swelling of cervical or axillary lymph nodes.        Thus, CFS diagnostic criteria are composed of two items of major criteria, and minor criteria (11 items of criteria of symptoms and 3 items of criteria of physical findings). CFS has been diagnosed when the following requirements are satisfied; satisfaction of 8 items or more of criteria of symptoms (of minor criteria) in addition to two items of major criteria, or satisfaction of at least 6 items of criteria of symptoms and at least 2 items of criteria of physical findings, in addition to two items of major criteria. When two items of major criteria are satisfied, but the requirements are not satisfied in minor criteria, then it is evaluated “doubtful (pseudo) CFS.” Among the CFS diagnosed by the above criteria, if the symptom of the CFS appeared following the infectious disease, then it is called “postinfectious CFS.”        
The above-mentioned CFS diagnostic method, however, depends on the clinical findings and opinions by the doctor. Therefore, more objective CFS diagnostic method is needed, which does not need skill and experience.
Currently, a component analysis using near infrared spectroscopy is being carried out in various fields. For example, a sample is irradiated with visible light and/or near-infrared rays, a wavelength range in which the visible light and/or near-infrared rays are absorbed by a specific component is detected, and the specific component is then analyzed quantitatively.
This is carried out as follows: for example, a sample is injected into a quartz cell, and this is irradiated with visible light and/or near-infrared rays in a wavelength range of 400 to 2500 nm, using a near-infrared spectroscope (such as an NIRSystem 6500 manufactured by Nireco Corp.); transmitted light, reflected light, or transmitted and reflected light is analyzed.
Generally, near-infrared rays have a very small absorbance coefficient to a substance, hardly undergo scattering, and are also a low-energy electromagnetic wave. Therefore they allow chemical/physical data to be obtained without damaging the sample.
Thus sample data can be obtained immediately by detecting, for example, transmitted light from a sample, determining the absorbance data of the sample, and subjecting this data to a multivariate analysis. For instance, the biomolecular structure or the process of change in its function can be obtained directly or in real time.
Examples of the conventional techniques relating to such near infrared spectroscopy include those described in patent documents 1 and 2 below. Patent document 1 discloses a method of obtaining data from a sample using visible and near-infrared rays, specifically, a method of discriminating the group to which an unknown sample belongs, a method of identifying an unknown sample, and a method of monitoring the time-dependent change in the sample in real time. This document does not disclose CFS diagnosis carried out by near infrared spectroscopy.
Patent document 2 discloses a method of diagnosing bovine mastitis by measuring a somatic cell in milk or the udder through a multivariate analysis of absorbance data obtained, using an absorption band of water molecules in the visible light and/or near-infrared region. Nonpatent document 2 discloses a clinical symptom of CFS and its mechanism considered.    [Nonpatent document 1] Tentative plan of CFS diagnostic criteria by Ministry of Health and Welfare, March, 1995.    [Nonpatent document 2] Adler R H. Chronic fatigue syndrome (CFS), Swiss Med Wkly. (2004) 134:268-76.    [Patent document 1] Japanese Laid-Open Patent Publication No. 2002-5827 (page 1-9, FIG. 1).    [Patent document 2] International Publication No. WO 01/75420 (page 1-5, FIG. 1).